As a power source for driving a motor of an electric car or the like, or as a power source for household use or industrial use, a battery block is used which is formed by interconnecting a plurality of cells such as lithium-ion cells in series or in parallel. A battery block used for high power application is charged and discharged at a high current, and the temperature of the cells increases. In such a case, in order to prevent the acceleration of cell degradation, it is preferable that the heat generated when each cell is charged and discharged is radiated efficiently and the cell performance is kept in a satisfactory state. For this purpose, for example, the following battery block is known. The arrangement surface of the cells is interposed between two radiation plates from both sides, and each radiation plate is brought into contact with the peripheral surfaces of the cells, thereby improving the heat radiation property from the surfaces of the cells (Patent Literature 1).